Diseases having a common pathological characteristic which a structure having a tau protein aggregate as a main constituent component develops in the brain are called tauopathies. Alzheimer's disease, frontotemporal dementia, Pick's disease, corticobasal degeneration, progressive supranuclear palsy, or the like are known as representative tauopathies.
Tauopathies are often accompanied by serious dementia, which has a large effect on patients and their families. Therefore, it is important to diagnose them at as early a stage as possible. Furthermore, the number of patients affected by these diseases has been increasing in recent years on a background of an aging society, and early diagnosis and therapy therefor have become matters of serious public concern.
As described above, a tau protein aggregate develops in the brain of tauopathy patients, and such a pathological change is thought to have an important role in the symptoms of these diseases. Therefore, much research for the purpose of diagnosis or treatment of a tauopathy has been carried out using an aggregated tau protein as a main target.
So far, various tau protein fibrosis inhibitors including rhodanines have been discovered as compounds having affinity toward a tau protein aggregate (non-patent document 1 and non-patent document 2). Furthermore, various quinoline derivatives and benzimidazole derivatives have been disclosed as biomarkers targeting a tau protein aggregate (non-patent document 3, patent document 1 and patent document 2).